1. Field of the Invention
The present invention is directed to the field of lamp assemblies and more specifically to such assemblies that are used in conjunction with license plate panels for illuminating surfaces of such panels.
2. Description of the Prior Art
A lamp assembly that is used to illuminate the surface of a flat panel, such as a license plate on an automotive vehicle, generally includes a reflective housing with an aperture for accepting a light bulb socket assembly and a lens element for allowing light to escape from the lamp assembly in various directions toward the front surface of the license plate. Such assemblies are generally effective for illuminating portions of the panel with varying intensities. The highest intensity of illumination usually occurs just adjacent to the lamp assembly, and the remote areas of the panel receive significantly less illumination.
U.S. Government regulations for illuminating license plates are expressed in Federal Motor Vehicle Safety Standards (FMVSS). Those standards mandate that eight test points on the plate be illuminated so that the ratio of illumination intensity measured at the two highest and the two lowest test points must not exceed 20:1 and that the minimum illumination per test point must be at least 0.75 Ft-c.
In order to comply with the standard, vehicle manufacturers generally use one of two approaches. The first approach uses two lamp assemblies to illuminate the license plate. In the two lamp assembly approach, the lamp assemblies are usually mounted above the top edge of license plate so that they will illuminate respective halves of the plate. The two lamp assemblies may also be mounted at opposite ends of the plate and direct light toward the center.
The second approach uses a single bulb lamp assembly, with a curved Fresnel lens mounted above or below the center of the plate to effect the distribution of light in a prescribed pattern. However, the second approach requires a relatively high intensity bulb to achieve the required illumination intensity.